Sensor arrangement

ABSTRACT

A sensor system ( 1; 20; 30; 40 ) is proposed for detecting forces which, particularly in the case of a motor vehicle, lead to a deformation of components, e.g. body parts ( 10 ) as the result of an accident. The sensor system ( 1; 20; 30; 40 ) has a number of contact elements ( 2, 3, 4; 21, 22, 23; 31, 32, 33 ) which are arranged on the component ( 10 ) staggered one behind the other in a possible deformation direction ( 11 ), compressible insulation layers ( 5, 6, 7; 24, 25; 35, 36 ) being disposed between the contact elements ( 2, 3, 4; 21, 22, 23; 31, 32, 33 ). The contact elements ( 2, 3, 4; 21, 22, 23; 31, 32, 33 ) are electroconductively connected to an electronic evaluation circuit by which a contacting and/or de-contacting of adjacent contact elements ( 2, 3, 4; 21, 22, 23; 31, 32, 33 ), caused by a deformation, is able to be detected and converted into control and or regulating signals.

BACKGROUND INFORMATION

[0001] The present invention relates to a sensor system, particularlyfor detecting mechanical forces which, for example, during a collisionof a motor vehicle with an obstacle, lead to an intrusion or deformationof components on this motor vehicle.

[0002] Such sensor systems are used, for example, for so-calledoccupant-restraint systems in motor vehicles which, for instance,trigger airbags accidents to protect the vehicle occupants from theresults of a collision. For triggering these occupant-restraint systems,for example, the acceleration in the passenger compartment or atperipheral regions of the motor vehicle is measured. In addition to thesensor or sensors in the passenger compartment, the peripheral sensorsare, as a rule, preferably installed at the deformable areas of thevehicle. Thus, for example, for better and early recognition of lateralcollisions, acceleration sensors are installed on the so-called B-pillarand/or C-pillar of the vehicle, or on the seat crossmembers below thefront seat.

[0003] In comparable manner, for better recognition of head-on crashes,sensors which likewise usually measure the acceleration and convert themeasured values into corresponding, electronically evaluable signals tobetter determine the severity of a crash are also built into the frontcrash crumple zone of the vehicle.

[0004] Particularly in the case of lateral collisions, the knownacceleration sensors have the disadvantage that they permit rapiddetection of a crash only if the sensor is directly struck. Thus, forexample, when installed on the B-pillar, a fixed-pole crash into thedoor of the vehicle is recognized too late. Pressure sensors, known bythemselves, also cause problems with respect to a separation of thetriggering and non-triggering conditions when installed at theselocations, since they should not respond, for instance, to heavy doorslamming. In the case of a triggering of driver and front-seat passengerairbags, as well, these pressure sensors must not interpret the pressurerise in the passenger compartment as deformation of the door.

[0005] Furthermore, in the case of a collision, the velocity of theintrusion by the obstacle is also a decisive factor which determines theseverity of the accident and the danger of injury for the occupants. Inthis context, the intrusion velocity is linked to the width of theobstacle and the location of the impact. For example, a post having asmall surface intrudes very deeply and quickly, while a wide barrierwhich impacts on the vehicle with the same velocity intrudes more slowlyand not as deeply. If the post strikes the middle of the door, itpenetrates considerably more quickly than if it strikes on the B-pillar. The wider an obstacle is, the more slowly it will penetrate, andthe softer the location of the impact, the deeper and more quickly itwill penetrate.

SUMMARY OF THE INVENTION

[0006] A sensor system mentioned at the outset for detecting forceswhich lead to a deformation of mechanical components, e.g., on motorvehicles, is advantageously further developed according to the presentinvention in that, according to the characterizing part of the mainclaim, provision is made chiefly on the possibly deformed components fora number of contact elements which are arranged staggered one behind theother in a possible deformation direction.

[0007] Insulation layers, which are compressible by the deformation ofthe component, are advantageously disposed between the contact elements.The contact elements are electroconductively connected to an electronicevaluation circuit by which a contacting and/or de-contacting ofadjacent contact elements, caused by the deformation, is then able to bedetected and converted into control and/or regulating signals.

[0008] In the sensor system according to the present invention, it isparticularly advantageous if one contact element represents a baseelement, and at least two contact elements are positioned in front of itat predefined distances. The distances, i.e. the geometricconfiguration, and the material for these two compressible insulationlayers are in each case selected so that the intrusion velocity of theobject causing the deformation is able to be derived from the moments ofthe contacting and or de-contacting of the contact elements situated onebehind the other in the deformation direction.

[0009] In the present invention, the compressible insulation layer made,for example, of foamed plastic, between the contact elements has thefunction of correctly defining the geometrical spacings of the contactelements. Therefore, the compression properties of the material, in thesame way as the temperature characteristic and the stiffness, is notcritical. In constructing the sensor system, care must only be takenthat the stiffness does not become so high over the course of theservice life of the sensor system that compression of the sensor systemis prevented. In most application cases, the deformation forcesoccurring are so considerable that an evaluable deformation is alreadyensured by them alone, even if the stiffness of the sensor system shouldvary.

[0010] The present invention permits the construction of a so-calledintrusion sensor for a motor vehicle which, in response to an accident,detects in a simple manner the penetration of an obstacle into thecomponents of the vehicle and, in so doing, allows determination of boththe velocity of the intrusion and the width of the impacting object, aswell as the location of the intrusion. The intrusion sensor itself isdeformed by the penetration, and the deformation is utilized to bringthe contact elements in contact with one another, it also being possibleto utilize the deformation itself for determining the severity of thecrash. Moreover, the intrusion sensor itself may be utilized as astructural element in such a way that the deformation characteristic ofthe vehicle may be influenced.

[0011] In addition to the lateral placement, such an intrusion sensormay also be used for detecting head-on collisions or rear collisions.For example, it is then mounted on the bumper between the bumper and theplastic cladding. In one such configuration, the sensor measures therelative velocity of the crash, and the width of the obstacle and thelocation of the impact may again be determined. For example, using thisintrusion sensor, it is then possible to obtain information about theimpacting obstacle, as well.

[0012] The signals generated by the contact elements are evaluated in asimple manner by connecting the contact elements, e.g., via an RCcircuit, directly to a microprocessor of the electronic evaluationcircuit, the microprocessor being able to directly measure the moments,e.g. T₁ and T₂, mentioned above. However, moments T₁ and T₂ may also bedetermined by charging a capacitor, and sent as coded informationdirectly to an analyzing unit, e.g. an airbag control unit in a motorvehicle.

[0013] For the contact elements to come reliably in contact, the sensorsystem must also really be deformed. Misuse conditions such as hammerblows and striking the door will as a rule not deform the sensor to theextent that both contact elements are closed. The misuse problems, whichare to some extent very serious for the known acceleration or pressuresensors, are substantially prevented by the present invention. If, forexample, the sensor is structurally mounted near a reinforcement tube inthe door of a motor vehicle, then the safety with respect to misuseconditions is again increased.

[0014] In the following, advantageous specific embodiments of thepresent invention are indicated having configurations of the contactelements and of the insulation layers, as well as of an RC circuit,designed for particular application cases.

[0015] In these specific embodiments, the compressible insulation layersare arranged in at least one partial area of the surface of the contactelements, and in the area remaining in each case, a contact is able tobe produced with the adjacent contact element by compression of theinsulation layer and/or by deformation of the respective contactelement.

[0016] In a first specific embodiment, the insulation layers between thecontact element situated at the top in the deformation direction and themiddle contact element are disposed in at least one lateral partialarea, and the insulation layers between the middle contact element inthe deformation direction and the base element are arranged in twoopposite lateral partial area.

[0017] The contact elements are provided geometrically here such thatelectrical contact is ensured in response to complete compression of theinsulation layer; this may be additionally supported by suitable bars onthe base element and, if desired, on the other contact elements, aswell. The base contact element itself may also be formed geometricallyso that it has an elevation in the middle. This elevation must be sohigh that it corresponds approximately to the thickness of thecompressible material in the completely compressed state.

[0018] In another specific embodiment, the insulation layer between thecontact element situated at the top in the deformation direction and themiddle contact element is disposed in one lateral partial area, and theinsulation layer between the middle contact element in the deformationdirection and the base element is arranged in the same lateral partialarea.

[0019] Thus, in this case, the actual contact surfaces are situatedspatially next to the compressible areas. In this context, the basecontact element is constructed such that it is stable enough so that theupper and the middle contact elements and the compressible material arepressed together for the contacting first, before the base element isbent. So that the sequence of the compression remains defined, it isadvantageous to select a stiffness for the first insulation layer in theregion between the upper and the middle contact elements which is lessthan that of the second insulation layer in the region between themiddle contact element and the base element. This ensures that the upperand the middle contact elements are closed first before the secondinsulation layer is compressed at moment T₂.

[0020] In a further specific embodiment, at least two contact elementsare made of partial contact elements which, in the quiescent state, lieside by side, contacting. The compressible insulation layers arearranged in at least one partial area of the surface of the at least twocontact elements, and in the area remaining in each case, ade-contacting, i.e. opening of the partial contact elements is able tobe effected by compression of the insulation layer and/or by deformationof the respective contact element.

[0021] With this specific embodiment, an intrusion sensor may beimplemented in that, due to the intrusion of an object and the resultingcompression, the upper contact element is pressed, for example, by wayof an electrically insulating spacer, onto a first closed contact of themiddle contact element. In this context, the upper contact element isformed geometrically so that the contact of the middle contact elementis opened. If the sensor system is further compressed, then the middlecontact element and an electrically insulating spacer press on a lowercontact element on the base element and open it. The intrusion velocitymay then in turn be determined from the time interval of this opening.

[0022] For a particularly advantageous evaluation, the upper contactelement and the base contact element may be made of a magnetic material,and the middle contact element may be a flat coil. In this case, acontacting of the contact elements leads to a change in the impedancebetween the upper and the middle and between the middle and the basecontact element. The closing of the contact elements may also bedetected by one or more Hall sensors. According to one advantageousfurther development, permanent magnets are provided in the upper contactelement and in the base contact element. The contacting of the upper andmiddle contact elements and/or of the middle and the base contactelements is easily detectable by a contact of the Hall sensors with thepermanent magnets.

[0023] In another specific embodiment, the contact elements may beformed by two planar-like fracture ceramics which in each case areseparated by a compressible insulation layer. The fracture ceramics areprovided here with an electroconductive path or layer whose interruptionis detectable. In this case, an interruption in response to theintrusion of an object defines moment T of the impact. A fracture of theupper ceramic moment T₁ of the impact, and the fracture of the lowerceramic moment T₂. It is then possible to determine the intrusionvelocity from the time difference between T₁, and T₂ and the thicknessof the compressible insulation layer.

[0024] It is also advantageous if at least the upper and the middlecontact elements are divided in a direction, preferably the longitudinaldirection, into a plurality of contact regions, where in each case pairsof upper and middle contact elements are connected via separate lines tothe evaluation circuit.

[0025] Information about the location of the deformation may also beobtained due to this division. Between the respective matching pairs,the intrusion velocity may now also be determined nearly independentlyfor each partial area of the sensor system, and the width of theintruding object may be determined from the number of compressedsubdivisions. Moreover, the location of the primary intrusion may alsobe determined from the time sequence of the closing of the respectivecontact pairs.

[0026] The already mentioned protective circuit in the connection of thecontact elements may be implemented in a simple manner by a resistornetwork in which, for example, a parallel resistor situated in each casebetween the upper and the middle and the middle and the base contactelement, as well as a series resistor leading from the middle contactelement are applied. The series resistor is connected by a first line,and the joined connection terminals of the upper and the base contactelements are connected by a second line to the evaluation circuit.

[0027] If the contact elements are subdivided into a plurality ofsub-regions, a resistor network may again be implemented, in which thecontact elements are connected to the evaluation circuit via a resistornetwork, where in each of the divided contact regions, a parallelresistor is situated between the upper and the middle contact element.These parallel resistors are connected in series in the direction of thedivided regions, and the outer connection terminals of this seriescircuit are run to the evaluation circuit. With this, it is alsopossible to reduce the number of lines via which the sensor system isconnected to the evaluation circuit, without the evaluation capabilitysuffering.

[0028] The surfaces of the contact areas of the contact elements may betreated in such a way that no erosion can take place and the closing ofthe contacts is also ensured over the entire service life of the sensorsystem. Since, when used in the motor vehicle, the sensor system is alsoable to be mounted in the door or on the bumper of the motor vehicle,the sensor system may also be enclosed in a simple manner by awaterproof casing which, however, must permit a deformation withouthindrance. For example, this casing may be a thin rubber casing whichhermetically seals the sensor, but permits compression and a pressureequalization in response to temperature fluctuations. For example, theentire sensor system may also be incorporated into a casing of thin,easily deformable metal, such as a thin aluminum casing.

[0029] These and other features of preferred further developments of theinvention, in addition to being derived from the claims, are alsoderived from the specification and the drawings; the individualfeatures, each by itself alone or combined in the form ofsub-combinations, are able to be implemented in the specific embodimentof the invention and in other fields, and are able to representembodiments which are advantageous as well as patentable by themselves,for which protection is claimed here.

BRIEF DESCRIPTION OF THE DRAWING

[0030] Exemplary embodiments of the sensor system according to thepresent invention are explained with reference to the drawing, in which:

[0031]FIG. 1 shows a schematic representation of a first exemplaryembodiment, in which the sensor system is mounted as an intrusion sensorin the door of a motor vehicle;

[0032]FIG. 2 shows a second exemplary embodiment with a modification ofthe arrangement of contact elements and insulation layers in theintrusion sensor according to FIG. 1;

[0033]FIG. 3 shows a third exemplary embodiment with a modification ofthe arrangement of contact elements and insulation layers in theintrusion sensor according to FIG. 1, in which the contact elements areopened by a deformation;

[0034]FIG. 4 shows an intrusion sensor according to FIG. 1 having aresistor network as RC circuit;

[0035]FIG. 5 shows a further exemplary embodiment of an intrusion sensorhaving regions of the contact elements that are distributed in thelongitudinal direction and are connected via a resistor network; and

[0036]FIG. 6 shows an intrusion sensor according to FIG. 5 having anexpanded resistor network.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0037] An exemplary embodiment of a sensor system 1 according to FIG. 1shows an upper electroconductive contact element 2, a middleelectroconductive contact element 3 and a third electroconductivecontact element 4 as base element. Situated between contact elements 2,3 and 4 are compressible insulation layers 5, 6 and 7 made, for example,of foamed plastic, which spatially separate contact elements 2, 3 and 4at a predefined distance, distance D between middle contact element 3and base element 4 in particular being significant here for theevaluation of the sensor signals.

[0038] Sensor system 1 is installed, for example, in door trim 10 of amotor vehicle (not shown here), and is able to be deformed in adirection 11 during an accident. Contact elements 2, 3 and 4, possiblywith bars 8 and 9, are provided in such a way that an electrical contactis ensured between these elements 2, 3 and 4 in response to completecompression of insulation layers 5, 6 and 7 because of a crash.

[0039] Sensor system 1 may be installed, for example, on the inside ofthe motor-vehicle door below the reinforcing tube; sensor system 1 maycover the entire length of the door, for example, from the front stop atthe so-called A-pillar up to the door lock. If door trim 10 is nowpressed in by an impact of an object, then upper contact element 3 ispressed onto middle contact element 4 and is contacted to it, so thatmoment T₁, of the contacting may be detected via lines 12, 13 and 14connected to these contact elements 2, 3 and 4. The obstacle thenpenetrates further and finally presses upper and middle contact elements2 and 3 onto base element 4. The contact between middle contact element3 and base element 4 is then closed at a moment T₂.

[0040] Intrusion velocity V_(i) of the object may then be ascertainedfrom the known distance D between middle contact element 3 and baseelement 4, and moments T₁, and T₂ according to the equation

V _(i) =D/(T ₂ −T ₁)  (1)

[0041] Typically, distance D is, let us say, 2 cm, with which at avelocity of 20 m/s (corresponding to 72 km/h) a time difference T₂−T₁ of0.02/20 sec corresponding to 1 ms results. This time difference permitsboth a direct measurement by a microprocessor in the evaluation circuit,as well as a rapid triggering of actuators in the vehicle, such as, forexample, an airbag.

[0042] In an exemplary embodiment according to FIG. 2, an intrusionsensor 20 is provided with contact elements 21, 22 and 23 which, in amodification with respect to FIG. 1, are in each case provided on oneside with an insulation layer 24 and 25. Intrusion velocity V_(i) isdetermined here in the same manner as in the exemplary embodimentaccording to FIG. 1.

[0043]FIG. 3 shows an exemplary embodiment of a sensor system 30 inwhich an upper contact element is implemented as pressure plate 31. Amiddle contact element 32 and a lower contact element 33 are alsoprovided on a base plate 34. Contact elements 32 and 33 are made ofpartial contact elements which, in the quiescent state, lie side byside, contacting. Compressible insulation layers 35 and 36 are appliedbetween contact elements 31 and 32 and between 33 and 34.

[0044] In this case, contact elements 32 and 33 open by compression ofinsulation layers 35 and 36 in response to a deformation of sensorelement 30. Upon intrusion of an object and the resulting compression ofinsulation layers 35 and 36, upper pressure plate 31 presses on a firstclosed contact of middle contact plate 32. Pressure plate 31 is formedgeometrically so that the contact of middle partial contact elements 32is opened, for example, by way of an electrically insulating elevation37. If the sensor system is further compressed, then middle contactelement 32 and an electrically insulating elevation 38 press on lowercontact element 33 and open the contact here. As mentioned above,intrusion velocity V_(i) may again be determined from the time intervalof the opening.

[0045] As mentioned above, it is useful if contact elements 2, 3, 4; 21,22, 23 or 31, 32, 33 are able to be connected via an RC circuit directlyto the microprocessor of the evaluation circuit, the microprocessorbeing able to directly measure times T₁, and T₂. FIG. 4 shows an examplefor implementing a resistor network in conjunction with sensor system 1described with reference to FIG. 1. Here, a resistor R₁, is positionedin parallel with respect to contact elements 2 and 3, and a resistor R₂is arranged in parallel with respect to contact elements 3 and 3. Fromcontact element 3, a series resistor R₃ goes to connection terminal 14.Therefore, series resistor R₃ is connected by a first line, and thejoined connection terminals of resistors R₁ and R₂ of upper and basecontact elements 2 and 3, respectively, are connected by a second linevia connection terminal 15 to the evaluation circuit.

[0046] Thus, in this exemplary embodiment, the closing of both contactscan be determined using only two connections of the evaluation circuitto sensor system 1. If no impact exists at this intrusion sensor 1, andtherefore exhibits no deformation, the total resistance is

R=R ₃+1/(1/R ₁+1/R _(l)).  (2)

[0047] In the event of an impact, then initially the upper contactbetween contact elements 2 and 3 is closed. The total resistance is then

R=R ₃ +R ₂.  (3)

[0048] If sensor system 1 is further deformed and the lower contactcloses, then the total resistance is

R=R₁.  (4)

[0049] If the total length of a sensor circuit 40 according to FIG. 5 isdivided into a plurality of narrower regions 41, 42, 43 and 44, then itis also possible to obtain information about the location of adeformation. To that end, the upper and middle contact elements are ineach case divided here into a plurality of regions, so that betweenrespective matching pairs of upper and middle contact element and thelower base element, the intrusion velocity may now be determined nearlyindependently for each partial region 41, 42, 43 and 44 of sensor system40.

[0050] The width of the intruding object may be determined from thenumber of compressed regions 41, 42, 43 or 44, and the location of theprimary intrusion may be determined from the time sequence of theclosing of the respective pairs of contact elements. The resistornetwork according to FIG. 5 usable here, in each of divided regions 41,42, 43 and 44, contains a parallel resistor R₁₁, R₁₂; R₂₁, R₂₂; R₃₁, R₃₂and R₄₁, R₄₂ in each case between the upper and the middle contactelement and the middle and the base element. These parallel resistorsare connected in series in the direction of the divided regions, and theouter connection terminals of this series circuit are connected to theevaluation circuit via connection terminals 45 and 46.

[0051]FIG. 6 shows a modification of the resistor network according toFIG. 5, where the resistor pairs of parallel resistor R₁₁, R₁₂; R₂₁,R₂₂; R₃₁, R₃₂ and R₄₁, R₄₂ are run on one side in parallel via a seriesresistor R₁₀, R₂₀, R₃₀ and R₄₀, as well as a total series resistor R₀ toconnection terminal 46, and with the other side directly to connectionterminal 45.

What is claimed is:
 1. A sensor system for detecting forces which leadto a deformation of mechanical components (10), wherein the sensorsystem (1; 20; 30; 40) has a number of contact elements (2, 3, 4; 21,22, 23; 31, 32, 33) which are arranged on the component (10) staggeredone behind the other in a possible deformation direction (11),compressible insulation layers (5, 6, 7; 24, 25; 35, 36) being disposedbetween the contact elements (2, 3, 4; 21, 22, 23; 31, 32, 33), and thecontact elements (2, 3, 4; 21, 22, 23; 31, 32, 33) areelectroconductively connected to an electronic evaluation circuit bywhich a contacting and/or de-contacting of adjacent contact elements (2,3, 4; 21, 22, 23; 31, 32, 33), caused by a deformation, is able to bedetected and converted into control and/or regulating signals.
 2. Thesensor system as recited in claim 1, wherein one contact elementrepresents a base element (4; 23; 33, 34), and at least two contactelements (4; 21, 22; 31, 32) are arranged at predefined distances (D)thereto, the distances (D) or the at least two compressible insulationlayers (5, 6, 7; 24, 25; 35, 36) being configured in each case so thatthe intrusion velocity (V_(i)) of the object causing the deformation isderivable from moments (T_(l), T₂) of the contacting and/orde-contacting of the contact elements (2, 3, 4; 21, 22, 23; 31, 32, 33)situated one behind the other in the deformation direction.
 3. Thesensor system as recited in claim 1 or 2, wherein the compressibleinsulation layers (5, 6, 7; 24, 25; 35, 36) are arranged in at least onepartial area of the surface of the contact elements (2, 3, 4; 21, 22,23; 31, 32, 33), and in the area remaining in each case, a contact isable to be effected with the adjacent contact element (2, 3, 4; 21, 22,23; 31, 32, 33) by compression of the insulation layer (5, 6, 7; 24, 25;35, 36) (and/or by deformation of the respective contact element . . .?).
 4. The sensor system as recited in claim 1 or 2, wherein at leasttwo contact elements (32, 33) are made of partial contact elementswhich, in the quiescent state, lie side by side, contacting, and thecompressible insulation layers (35, 36) are arranged in at least onepartial area of the surface of the at least two contact elements (32,33), and in the area remaining in each case, the partial contactelements being able to be decontacted by compression of the respectiveinsulation layer (35, 36) (and/or by deformation of the respectivecontact element . . . ?).
 5. The sensor system as recited in claim 3 or4, wherein the insulation layer (5) between the contact element (2)situated at the top in the deformation direction and the middle contactelement (3) is arranged in at least one lateral partial area, and theinsulation layers (6, 7) between the middle contact element (3) in thedeformation direction and the base element (4) are arranged in twoopposite lateral partial area.
 6. The sensor system as recited in claim3, wherein the insulation layer (24) between the contact element (21)situated at the top in the deformation direction and the middle contactelement (22) is arranged in a lateral partial area, and the insulationlayer (25) between the middle contact element (22) in the deformationdirection and the base element (23) is arranged in the same lateralpartial area.
 7. The sensor system as recited in one of the precedingclaims, wherein the compressible insulation layers (5, 6, 7; 24, 25; 35,36) are made of foamed plastic.
 8. The sensor system as recited in oneof claims 2 through 7, wherein the upper contact element and the basecontact element are made of a magnetic material, and the middle contactelement is a flat coil, a contacting of the contact elements leading toa change in the impedance between the upper and the middle, and betweenthe middle and the base contact element.
 9. The sensor system as recitedin one of the preceding claims, wherein the contacting of the contactelements is detected by Hall sensors.
 10. The sensor system as recitedin claim 9, wherein one or more Hall sensors are mounted on the middlecontact element, and permanent magnets are provided in the upper contactelement and in the base contact element, the contacting of the upper andmiddle contact elements and/or of the middle and base contact elementsbeing detectable by a contact of the Hall sensors with the permanentmagnets.
 11. The sensor system as recited in one of claims 1 through 7,wherein the contact elements are formed by two planar-like fractureceramics which are separated by a compressible insulation layer, and thefracture ceramics are provided with an electroconductive path whoseinterruption is detectable.
 12. The sensor system as recited in one ofthe preceding claims, wherein in a subdivided sensor system (40), atleast the upper and the middle contact elements are divided in onedirection, preferably the longitudinal direction, into a plurality ofregions (41, 42, 43, 44), in which pairs of upper and middle contactelements are in each case connected via separate lines to the evaluationcircuit.
 13. The sensor system as recited in one of the precedingclaims, wherein the contact elements are connected to the evaluationcircuit via a resistor network.
 14. The sensor system as recited inclaim 13, wherein the resistor network is made of parallel resistor (R₁,R₂), situated in each case between the upper and the middle and betweenthe middle and the base contact element, as well as a series resistor(R₃) leading from the middle contact element, and the series resistor(R₃) is connected by a first line, and the joined connection terminalsof the upper and of the base contact elements (2, 4) are connected by asecond line via connection terminals (13, 15) to the evaluation circuit.15. The sensor system as recited in claim 12, wherein the contactelements are connected to the evaluation circuit via a resistor networkin which, in each of the divided regions (41, 42, 43, 44) a parallelresistor (R₁₁, R₁₂; R₂₁, R₂₂; R₃₁, R₃₂; R₄₁, R₄₂) is situated betweenthe upper and the middle contact elements, and these parallel resistors(R₁₁, R₁₂; R₂₁, R₂₂; R₃₁, R₃₂; R₄₁, R₄₂) are connected in series in thedirection of the divided regions (41, 42, 43, 44), and the outerconnection terminals (45, 46) of this series-circuit are run to theevaluation circuit.
 16. The sensor system as recited in claim 12,wherein the contact elements are connected to the evaluation circuit viaa resistor network in which, in each of the divided regions (41, 42, 43,44) a parallel resistor (R₁₁, R₁₂; R₂₁, R₂₂; R₃₁, R₃₂; R₄₁, R₄₂) issituated in each case between the upper and the middle contact elements,and pairs of these parallel resistors (R₁₁, R₁₂; R₂₁, R₂₂; R₃₁, R₃₂;R₄₁, R₄₂) belonging to one of the regions (41, 42, 43, 44) are routed atone end via a series resistor (R₁₀; R₂₀; R₃₀; R₄₀) and jointly via atotal series resistor (R₀) to the connection terminal(46), in each caseat the other end to the connection terminal (45) for the evaluationcircuit.
 17. The sensor system as recited in one of the precedingclaims, wherein the contact elements (2, 3, 4; 21, 22, 23; 31, 32, 33)are covered with a corrosion-protection coating, and the sensor system(1; 20, 30, 40) is covered with a moisture-proof protective film,preferably of rubber elastic material.
 18. The sensor system as recitedin one of claims 1 through 16, wherein the entire sensor system (1; 20,30, 40) is enclosed by a hermetically sealed metal casing made of thin,soft, easily compressible metal, and has a moisture-proof electricalconnection to the outside.